Package java.awt.dnd

拖放是在许多图形用户界面系统中发现的直接操纵手势，它提供了一种在逻辑上与GUI中的表示元素相关联的实体之间传递信息的机制。

See: 描述

接口摘要

接口	描述
Autoscroll	在DnD操作期间，用户可能希望将操作的主题放在用户当前不可见的可滚动GUI控件的区域上。
DragGestureListener	用于接收拖动手势事件的侦听器界面。
DragSourceListener	DragSourceListener定义了用于跟踪用户手势状态的拖放操作的 DragSourceListener的事件接口，并在拖放操作中向用户提供适当的“拖拽”反馈。
DragSourceMotionListener	用于在拖动操作期间接收鼠标运动事件的侦听器界面。
DropTargetListener	DropTargetListener接口是 DropTarget类使用的回调接口，用于提供涉及主题 DropTarget的DnD操作的 DropTarget 。

类摘要

类	描述
DnDConstants	此类包含表示由拖放操作执行的操作类型的常量值。
DragGestureEvent	DragGestureEvent被传递给 DragGestureListener的dragGestureRecognized（）方法，当特定的 DragGestureRecognizer检测到正在跟踪的 Component上发生平台依赖的拖动启动手势时。
DragGestureRecognizer	DragGestureRecognizer是一个用于指定与平台相关的监听器的抽象基类，可以与特定的Component相关 Component ，以便识别平台相关的拖动启动手势。
DragSource	DragSource是 DragSource操作的实体，可用于多种情况：在该JVM的生命周期中每个JVM使用1个默认实例。
DragSourceAdapter	用于接收拖动源事件的抽象适配器类。
DragSourceContext	DragSourceContext类负责管理拖放协议的发起方。
DragSourceDragEvent	该 DragSourceDragEvent从交付 DragSourceContextPeer ，通过 DragSourceContext ，到 DragSourceListener与注册 DragSourceContext和与其相关 DragSource 。
DragSourceDropEvent	所述 DragSourceDropEvent被从递送 DragSourceContextPeer ，经由 DragSourceContext到 dragDropEnd的方法 DragSourceListener与注册小号 DragSourceContext和与其相关联的 DragSource 。
DragSourceEvent	这个类是 DragSourceDragEvent和 DragSourceDropEvent的基类。
DropTarget	该 DropTarget与相关 Component时 Component希望接受拖放操作期间下降。
DropTarget.DropTargetAutoScroller	这个受保护的嵌套类实现自动滚动
DropTargetAdapter	用于接收丢弃目标事件的抽象适配器类。
DropTargetContext	甲 DropTargetContext每当用拖放操作相关联的逻辑光标用的可见几何一致创建 Component与相关联的 DropTarget 。
DropTargetDragEvent	所述 DropTargetDragEvent被输送到 DropTargetListener经由其dragEnter事件（）和的dragover（）方法。
DropTargetDropEvent	所述 DropTargetDropEvent经由递送 DropTargetListener降（）方法。
DropTargetEvent	DropTargetEvent是 DropTargetDragEvent和 DropTargetDropEvent的基础类。
MouseDragGestureRecognizer	DragGestureRecognizer这个抽象子类定义了一个基于鼠标的手势的 DragGestureRecognizer 。

异常摘要

异常	描述
InvalidDnDOperationException	java.awt.dnd包中的各种方法抛出此异常。

Package java.awt.dnd Description

Drag and Drop is a direct manipulation gesture found in many Graphical User Interface systems that provides a mechanism to transfer information between two entities logically associated with presentation elements in the GUI. Normally driven by a physical gesture of a human user using an appropriate input device, Drag and Drop provides both a mechanism to enable continuous feedback regarding the possible outcome of any subsequent data transfer to the user during navigation over the presentation elements in the GUI, and the facilities to provide for any subsequent data negotiation and transfer.

This package defines the classes and interfaces necessary to perform Drag and Drop operations in Java. It defines classes for the drag-source and the drop-target, as well as events for transferring the data being dragged. This package also provides a means for giving visual feedback to the user throughout the duration of the Drag and Drop operation.

A typical Drag and Drop operation can be decomposed into the following states (not entirely sequentially):

• A DragSource comes into existence, associated with some presentation element (Component) in the GUI, to initiate a Drag and Drop of some potentially Transferable data.
  
  
• 1 or more DropTarget(s) come into/go out of existence, associated with presentation elements in the GUI (Components), potentially capable of consuming Transferable data types.
  
  
• A DragGestureRecognizer is obtained from the DragSource and is associated with a Component in order to track and identify any Drag initiating gesture by the user over the Component.
  
  
• A user makes a Drag gesture over the Component, which the registered DragGestureRecognizer detects, and notifies its DragGestureListener of.

  Note: Although this API consistently refers to the stimulus for a drag and drop operation being a physical gesture by a human user, this does not preclude a programmatically driven DnD operation given the appropriate implementation of a DragSource. This package contains the abstract class MouseDragGestureRecognizer for recognizing mouse device gestures. Other abstract subclasses may be provided by the platform to support other input devices or particular Component class semantics.
  
  

• The DragGestureListener causes the DragSource to initiate the Drag and Drop operation on behalf of the user, perhaps animating the GUI Cursor and/or rendering an Image of the item(s) that are the subject of the operation.
  
  
• As the user gestures navigate over Component(s) in the GUI with associated DropTarget(s), the DragSource receives notifications in order to provide "Drag Over" feedback effects, and the DropTarget(s) receive notifications in order to provide "Drag Under" feedback effects based upon the operation(s) supported and the data type(s) involved.

The gesture itself moves a logical cursor across the GUI hierarchy, intersecting the geometry of GUI Component(s), possibly resulting in the logical "Drag" cursor entering, crossing, and subsequently leaving Component(s) and associated DropTarget(s).

The DragSource object manifests "Drag Over" feedback to the user, in the typical case by animating the GUI Cursor associated with the logical cursor.

DropTarget objects manifest "Drag Under" feedback to the user, in the typical case, by rendering animations into their associated GUI Component(s) under the GUI Cursor.

The determination of the feedback effects, and the ultimate success or failure of the data transfer, should one occur, is parameterized as follows:

• By the transfer "operation" selected by the user, and supported by both the DragSource and DropTarget: Copy, Move or Reference(link).
  
  
• By the intersection of the set of data types provided by the DragSource and the set of data types comprehensible by the DropTarget.
  
  
• When the user terminates the drag operation, normally resulting in a successful Drop, both the DragSource and DropTarget receive notifications that include, and result in the type negotiation and transfer of, the information associated with the DragSource via a Transferable object.

从以下版本开始：

1.2